1. Field of the Invention
This invention relates to a monoclonal antibody recognizing the C-terminus of hBNP, a hybridoma producing the monoclonal antibody, a method of producing the monoclonal antibody comprising cultivating the hybridoma in a medium or an abdominal cavity of a mouse and recovering said monoclonal antibody from said medium or ascites in said abdominal cavity, and an immunoassay for hBNP with use of said monoclonal antibody.
2. Related Art
Brain natriuretic peptide (BNP) in the porcine brain was first reported by Matsuo et al, Nature 332, 78-81 (1988). There exist porcine (p) BNP-26 of 26 amino acid residues and pBNP-32 of 32 residues. These has peripheral and central actions similar to those of atrium natriuretic peptide (ANP) and play an important role in the homeostasis of body fluid and the control of blood pressure together with ANP. BNP was suggested to be produced in and secreted from the heart in human (Biochem. Biophys. Res. Commun. 159, 1427-1434 (1989)), and BNP in the human heart has recently be isolated and characterized (FEBS Lett. 259, 341-345 (1990)). Human BNP (hBNP) comprises 32 amino acid residues identical with the sequence 77-108 of hBNP precursor.
As mentioned above, because BNP plays an important role in the homeostasis of body fluid and the control of blood pressure, the determination of hBNP in the blood by an immunoassay etc. seems useful for diagnosing diseases such as hypertension and the like and states of heart, kidney and the like with taking an increase/decrease of hBNP level as an index. However, an average level of hBNP in the blood of normal adults is 0.9xc2x10.07 fmol/ml (3.12xc2x10.24 pg/ml) (J. Clin. Invest. 87, 1402-1412 (1991)) and such a low level has made it impossible to directly assay hBNP in the blood plasma without an extraction.
The inventors of this invention made an effort to solve the problem as mentioned above and succeeded in preparing a monoclonal antibody recognizing the C-terminus of hBNP and thereby establishing a specific sandwich radioimmunoassay for hBNP.
The immunoassay for hBNP provided by this invention is so sensitive that its minimum detection limit is 1 pg/ml and can therefore determine an hBNP level in plasma directly, that is, without extracting hBNP from plasma. It is useful for diagnosing diseases such as hypertension and the like and states of a heart, a kidney and the like with taking an increase/decrease of hBNP level as an index.